No current shipping unit defined for segment & (number &)

What causes this issue?

You attempted to define a packing hierarchy for a shipping unit that
does not exist. The error occurred in segment &V1& (segment number
&V2&). There may be a hierarchical problem in the IDoc.

System Response

The segment is not processed.

How to fix this error?

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Procedure for System Administrators

Error message extract from SAP system. Copyright SAP SE.